Fluid pump



J. c. FISHER 2,951,450

FLUID PUMP Sept. 6, 1960 2 Sheets-Sheet 1 Filed April 17, 1956 INVENTOR.OHN c. FISHER ATTORNEYS Sept. 6, 1960 .1. c. FISHER 2,951,450

FLUID PUMP Filed April 17, 1956 2 Sheets-Sheet 2 INVENTOR. JOHN C.FISHER ATTORNEYS FLUID PUMP John C. Fisher, 45 Sparks St., Cambridge,Mass.

Filed Apr. 17, 1956, Ser. No. 578,777

9 Claims. (Cl. 103223) This invention relates to an improved pumpparticularly suitable for use in transmitting corrosive fluids, toxic orinflammable fluids and fluids containing abrasive materials insuspension, and other fluids which cannot be satisfactorily handled byconventional pumps.

Displacement, rotary and centrifugal type pumps not only embody one ormore impellers and other moving parts with which the liquid being pumpedcomes in contact, but also a power-transmitting element driven from anexternal source. When such pumps are used to transmit corrosive liquids,solvents, etc. the moving parts and other surfaces coming in contactwith the liquid must either be made from a relatively costly,corrosive-resistant material, or they must be provided with a protectivecoating which after a relatively short period of use is apt to Wear orbecome stripped, thus introducing contamination into the liquid beingpumped. Moreover, since such pumps are driven from an external source itis necessary to use packing glands or the like seals which must beperiodically replaced in order to guard against leakage. Consequentlyboth the initial and maintenance costs of such pumps are relativelyhigh.

The principal objects of the present invention are to provide a pumpwhich has completely sealed fluid carrying members so that no leakage ispossible, such as might occur with conventional centrifugal, vane,piston or rotary pumps; to provide a pump having the aforementionedadvantages but which embodies a positive displacement action, asdistinguished from a non-positive displacement type such as disclosed inmy copending application Serial No. 553,015, filed December 14, 1955;and to provide a simple, effective and reliable means of eliminatingfrom the output of any type of fluid pump the pulsations of pressure anddischarge which are inherent in output of many conventional pumps, andalso of the pumps described herein.

More specific objects are to provide a pump capable of handling a fluidcontaining solid or abrasive particles, such as encountered in a coolantsystem for machine tools, to provide a pump which can safely handletoxic materials such as radio-active substances and highly inflammableor explosive fluids, etc., where leakage must be avoided, and to providea pump the output of which may be varied without using a valve or thelike.

Further objects will be apparent from a consideration of the followingdescription and the accompanying drawings, wherein:

Fig. l is a sectional elevation of a pumping system constructed inaccordance with the present invention;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a section on the line 3-3 of Fig. l; and

Fig. 4 is a schematic view of a modified form of the invention.

In accordance with the present invention I provide a pumping systemcomprising a pumping means operative to discharge into an externalcircuit, a pulsating unidirectional fluid flow and simultaneously drawin from an Patented Sept. 6, 1950 intake or a return line aunidirectional fluid flow, and a pressure-smoothing device connectedwith the discharge and inlet lines and operative to eliminate thepressure peaks from the pulsating fluid flow so as to obtain arelatively smooth or even pressure wave. The pumping means may compriseany conventional type of pump operative to discharge a unidirectionalpulsating fluid flow into a discharge line, or it may comprise a pump ofthe type shown in my aforesaid copending application operating inassociation with a fluid rectifier, but where a positive displacementaction is desired the pumping means prefenably comprise a pair ofcompressible chambers such as cooperating bellows, arranged so that whenone is compressed the other is expanded.

Where, as is preferred, bellows are employed they should be identicaland one end of each is completely closed and the otherend of each isformed with an output opening so that as the bellows are operated thereis induced an alternating or oscillating fluid flow through theirrespective output openings. These output openings are connected to afluid rectifier, such as shown in my copending application, so that theresultant flow is changed from an alteranting to a pulsating,unidirectional flow which is acted on by the smoothing device toeliminate the pressure peaks from the pulsating flow.

The pressure smoothing device comprises cooperating chambers constructedand arranged so that when one is expanded, the other is compressed. Eachof these chambers is provided with a single port and a relatively rigidduct connects the port of one chamber with the discharge line and asecond duct connects the other port with the intake or return lineleading to the pumping means. The cooperating chambers may comprise arelatively rigid enclosure divided by a flexible diaphragm so as todefine the cooperating chambers, the diaphragm being such as to respondto fluid pressure so as to expand or enlarge one chamber which receivesa fluid surge from one line and simultaneously compress the associatedchamber so as to force fluid through its port into the other line; orsuch cooperating chambers may comprise a pair of bellows, each havingbut a single opening, one communicating with the discharge line and theother communicating with the intake line.

Where the pressure smoothing device is thus connected in the system thesteady average component of the output pressure difierence causes thechamber connected with the low pressure or intake line to be compressed(i.e. decrease its internal volume) and the other chamber to expand(i.e. increase its internal volume) so as to admit a quantity of fluidfrom the discharge line, and the resultant of all the alternatingcomponents of the output pressure difference produces a purelyalternating motion about this average displaced position. Consequentlythe peaks of the pulsating fluid flow are, in effect, flattened out soas to fill in the troughs, as hereinafter more fully explained.

The various parts of the system may be made from any suitablecorrosion-resistant metal, a chemically inert plastic such as apolyamide (nylon), polyethylene, halogenated polyethylene (Teflon),polyvinylidene chloride (Saran), a suitable polyester or an epoxy resin,provided they possess the desired degree of rigidity, strength andfatigue resistance. In any case the particular material selected willdepend upon the type of fluid on which the pump is to operate, and thesesame considerations are applicable to the external circuit and partsassociated therewith.

Where bellows or the like compressible chambers constitute the pump, anysuitable means may be employed to a 3 this end one or moreelectrodynamic vibrators or the like may be used, or the mechanicalequivalent such as a crank, or other type of reciprocating motor.

Referring to Figs. 1 to 3, the embodiment shown there in comprisesessentially a positive displacement pump unit P connected with a fluidrectifier R having discharge and intake lines connected with thepressure smoothing device S. The pump P comprises a pair of spacedcircular plates land 2 which may be supported in any suitable manner andrigidly connected by a plurality of circumferentially spaced rods 4. Theplates 1 and 2 are provided with four pairs of circumferentially spacedaligned openings which receive bushings 5 and 6 and these bushingsslidably support four guide rods 8; The inner ends of these guide rodsare rigidly secured to a driving flange 18 and their opposite ends aresecured to a terminal ring 12.

Midway between the driving flange and terminal ring is a circularcrosshead'15 which is pinned or otherwise suitably secured to each ofthe guide rods. Each face of the crosshead is formed with a centrallydisposed circular recess and these recesses receive the inner closedends of a pair of identical coaxially disposed bellows l6 and 18 which,as above noted, may be of Teflon, corrosion-resistant metal or othersuit-able material. An adhesive or other suitable means anchors theclosed ends of the bellows in the circular recesses of the crosshead sothat one of the bellows is expanded and the other is contracted inresponse to movement of the crosshead. The opposite or open ends of thebellows are formed with circular gasket flanges 20 and 22 which contactthe plates 1 and 2, respectively. Cap screws 24 and 25, extendingthrough the plates 1 and 2 into compression rings 26 and 28, clamp theflanges against the plates so as to provide a fluid-tight joint.

The change of internal volume for a given linear displacement of eachbellows should be approximately equal on both compression and elongationof the bellows, and the two bellows units should be nearly identical toone another in this respect. If the volume-vs.-displacementcharacteristic of each bellows is not truly linear, then the stroke ofthe bellows relative to its normal length must be made small enough sothat a reasonable approximation to such a linear characteristic isobtained. For a given stroke, this can be achieved by using a suitablylarge number of convolutions in the bellows, so that the per-unitdisplacement of each convolution is small.

Each plate 1 and 2 is provided with a port or opening registering withthe opening in the bellows and these openings receive output ducts 3tand 3 2. Circumposed about the bellows and guide rods are helicalsprings 34 and 36, the ends of the spring 34 being seated in groovesformed in the plate 1 and the adjacent face of the crosshead 15 andthose of the spring 36 being similarly seated in grooves on the oppositeface of the crosshead and adjacent face of the plate 2. The effectivestiffness of the combination of the bellows, and the effective movingmass of these bellows, springs and crosshead are prop0r tioned so thatthe natural frequency of this moving system is equal or nearly equal tothe frequency of the reciprocating motion which is imparted to thesystem by the actuating means presently to be described.

The outer face of the drive flange is integral with spaced cars 38 whichcarry a wrist pin 40 that pivotally connects one end of a connecting rod42 to the drive flange. The other end of the connecting rod is pivotallyconnected by a crank pin 44 to a counterbalanced crank 45 mounted oncrankshaft 46 which is rotated or oscillated by any suitable mechanism(not shown) effective to impart oscillatory movement to the flange 10,guide rods 8 and crosshead 15.

As the crosshead 15 executes its motion, which is approximatelysinusoidal in its time-variation, bellows 16 is alternatively subjectedto increases and decreases in its internal volume, while bellows 18 issimultaneously subjected to equal and opposite changes of volume. Thus,each bellows alternately admits extra fluid on its expansion stroke andthen discharges this fluid on its compression stroke, both the entranceand exit of fluid taking place through the open port or duct to whichthe bellows is connected. It will be noted that there is no internalflow from one bellows to the other. Hence, in the conduits 30 and 32there is a purely reciprocating flow of fluid, which is rectified bymeans of the fluid rectifier R.

The fluid rectifier comprises a cylindrical block or body 48 having fourlongitudinally extending venturi-like passages 51, 52, 53 and 54-, theupper ends of the passages 52 and 53 being connected by a passage 57,and the upper ends of the passages 51 and 54 being connected by apassage 58. The lower ends of the passages 51 and 52 are connected by apassage 60 and the lower ends of the passages 53 and 54 are likewiseconnected by a passage 61. The passages 51 and 52 are provided with ballchecks 63 and 64 and each has a retainer pin, the arrangement being suchthat inward flow from the passage 60 is prevented, but outward flow tothe passage 60 is permitted. The passages 53 and 54 are also providedwith ball checks 65 and 66 and associated retainer pins, the arrangementbeing such that inward flow from the passage 61 is permitted, butoutward flow to the passage 61 is prevented. The duct 30 is connected bya line 68 with passage 58 and the duct 32 is connected by a line 70 withpassage 57. The passage 60 is connected to the discharge line 72 and thepassage 61 is connected with an intake 0 return line 74.

With this particular type of rectifier a pressure surge transmitted fromthe compressed bellows 16 to passage 58 forces fluid outwardly throughoutput passage 51 and simultaneously there will be a reverse surgecreated by the expansion of bellows 18 which draws fluid in throughinput passage 53 and passage 57. When the movements of the bellows arereversed a pressure surge transmitted from bellows 18 to the passage 57forces fluid outwardly through output passage 52 and simultaneously thereverse surge created by the expansion of bellows 16 draws fluidinwardly through input passage 54, thus producing a full waverectification.

Hence, fluid alternatingly surges outwardly through passages 57 and 58into discharge line 72 simultaneously with fluid alterna tingly surginginwardly from intake 74 through passages 53 and 54. Since the volume offluid transmitted in response to each surge is relatively small, beingless than the volume of the inlet and connecting passages, the path offlow is from the intake 74, connecting passage 61, then through inletpassages 53 and 54, along connecting passages 57 and 58, through outletpassages '51 and 52 to the connecting passage 60 and then to dischargeline 72, there being no unidirectional flow of fluid from bellows 16 tobellows 18 through the crosshead.

The discharge and intake lines 72 and 74 are connected with thepressure-smoothing device S which comprises a rigid cylindrical housing76 having rigid end plates 78 and 80 secured thereto by cap screwsextending through gaskets to provide a fluid tight chamber. The ends offour symmetrically disposed parallel guide rods 82 are secured to theend plates, and a circular crosshead 84, formed on each face withannular bosses 85 and 86 which carry guide bearings 88, is slidablysupported on the rods 82. The marginal portions of the crosshead 84 areprovided with a plurality of spaced openings 90 to permit fluid withinthe chamber readily to flow from one side of the crosshead to the other.The fluid within the housing 76 is preferably a low vapor pressure, lowkinematic viscosity, stable liquid which may be introduced into thehousing by removing one or more cap screws and replacing them after thehousing has been filled.

Each face of the crosshead 84 is formed with a centrally disposedcircular recess and these recesses receive the closed inner ends of apair-of identical coaxially disposed bellows 92 and 94 which may be ofthe same construction and material as the bellows 16 and 18 of the pump.An adhesive or other suitable means secures the ends of the bellows 92and 94 within the recesses so that as one is expanded the other iscontracted in response to a pressure surge. The opposite or open ends ofthe bellows are formed with circular gasket flanges 95 and 96 whichcontact the end plates 78 and 80, respectively. Cap screws 98 and 99,extending through the plates 78 and 80 into compression rings 101 and102 clamp the flanges against the plates so as to provide fluid tightjoints.

The plates 78 and 80 are formed with ports or openings registering withthe openings in the bellows and these ports receive ducts 104 and 105which are connected by Ts 106 and 108 to the intake and discharge lines74 and 72, respectively. Circumposed about the bellows, inwardly of theguide rods, are helical springs 110 and 112, the adjacent ends of whichabut the bosses 85 and 86 with their opposite ends seated in groovesformed on the inner faces of the plates 78 and 80. The effectivecombined stiffness of the helical springs and the bellows isproportioned relative to the effective moving mass of the bellows,springs and crosshead so that the natural frequency of this movingsystem in the absence of any damping force is equal or nearly equal totwice the basic frequency of the pumping unit. As hereinafter explained,this tuning of the moving system makes the magnitude of the pressurepulsation of twice the pump fre quency wholly dependent upon theinternal damping force, if any, of the smoothing device, and not uponthe characteristics of the pump or the nature of the external fluidcircuit. The motion of the crosshead now becomes predominantly adouble-frequency motion about an average position such that the staticforce of the combined stiffness just balances the average pressuredifference across the external fluid circuit. Hence, in ducts 104 and105 there is a purely alternating flow of fluid which is predominantly asinusoidal flow of twice the pump frequency.

The discharge line 72 may be connected to one or more distributing linesor any type of apparatus through which a steady, non-pulsating,unidirectional fluid flow is desired, and likewise the return or intakeline 74 may be connected to such apparatus, a reservoir or other meansfor supplying a fluid flow to the rectifier R.

Principle of operation In order more fully to appreciate the principlesand mode of operation of the above-described system we may assume thatthe motion of the crosshead is sinusoidal in its time-variation, thenthe discharge (i. e. the fluid volume per unit time emerging from thepump) will be a series of identical, consecutive half-sinusoids in thefluid conduits which connect the rectifier assembly to the externalfluid circuit. Such a waveform of fluid discharge is undesirable in manyapplications of this pump, and it is necessary in such cases to removethe pulsations from the external flow.

The pulsating discharge from the bellows pump P may be identicallyrepresented as the sum of the following components, which at eachinstant of time add algebracial- 1y .to yield the actual-instantaneousvalue of the discharge:

(1) A constant average value, which is the desired part of thedischarge;

.(2) A sinusoidal discharge of twice the frequency of the motion of thecrosshead of the pump;

(3) A sinusoidal discharge of 4 times the frequency of the motion of thecrosshead, and

(4-) An infinite series of simple harmonic discharge .waves, each ofhigher frequency andsmaller amplitude than the preceding one, withfrequencies which are even multiples of the fundamental frequency of thecrosshead. T

'6 1fthe desired average value of the discharge be de noted by thesymbol Q, then this Fourier series representation of the rectifiedsinusoid of instantaneous discharge 9 may be written mathematically ast=time n:2,4,6,8... It will be evident from inspection of this equationthat the major elements of the pulsation in the discharge are thesinusoidal components of twice the basic frequency and 4 times the basicfrequency, which is denoted by f in the equation. The amplitudes of thesecond, 4th and 6th harmonics, relative to the average value are,respectively, 0.6667, 0.13333, and 0.05714. Hence, if we elimimate the2nd and 4th harmonics from the total discharge, we have a substantiallyuniform flow. Of course, if we wish a very smooth output, we musteliminate all harmonic components up through the 20th, for which therelative amplitude is 0.005012, an entirely negligible quantity forpractical purposes.

It is thus possible to obtain virtually perfect elimination of any oneharmonic component of the discharge represented by the above equation,and hence, by reiteration of this means, to eliminate any desired numberof the harmonic components of the discharge. This unit, of course, ispassive, in that it has no external prime mover, but is set into motionof a reciprocating nature by virtue of the pulsations in the pressurediiference between its open ports.

It will be noted that the particular unit above described differs fromthe assembly used for pumping in only two significant ways:

(1) It is entirely enclosed in a leakproof container of some suitablemetal or plastic material, which is filled with a chemically inert,incompressible liquid in such a way that there are no voids in the spaceoutside the bellows units but within the container.

(2) The relative magnitudes of the effective moving mass and the neteffective stiffness of the springs and bellows units are such that thenatural frequency of the moving system is equal to or nearly equal tothe frequency of the lowest harmonic component of this discharge, ortwice the frequency of the pumping unit.

'When this assembly is connected in shunt across the output and returnconduits from the fluid rectifier, the steady average component of theoutput pressure difference will cause the crosshead 84 to be displacedtoward the bellows 92 which is connected to the low-pressure (return)conduit. The resultant of all the alternating components of the outputpressure difference will cause the crosshead to execute -a purelyalternating motion about this average displaced position. As. thecrosshead moves in this fashion, the forces which are exerted upon itfrom without itself arethe following:

A. The resultant of the internal fluid pressures transmitted through theclosed ends of the bellows units;

B. The resultant of the forces exerted through the closed bellows endsdue to the inherent stiffness of the bellows units themselves;

C. The resultant of the forces due to the springs;

D. The resultant of the liquid pressure exerted by the liquid whichfills the container.

Where, as here shown, the annular space between the rim of the crosshead84 and the housing wall is large and the outer portion of thecrosshead-is provided with several openings 90, then the filler liquidcan move freely around and through the crosshead, and force D can bemade as small as desired.

According to Newtons law, the net acceleration of the moving crossheadis equal-to the sum of forces A, B, C and D, divided by the effectivemass of the moving system. Now the acceleration of the crosshead is areciprocating one consisting of a Fourier series of harvolume of theother bellows.

monic accelerations, and at twice the basic frequency of the pump, thiscomponent of acceleration is just provided for by the sum of forces Band C. Hence, for this double-frequency acceleration, force A must beequal and opposite to force D, since the unit is in mechanical resonanceat twice the basic frequency. Therefore, by making the damping force dueto the filler liquid as small as desired, I can correspondingly reducethe alternating Component of pressure dilference between the dischargeconduit and the intake conduit of the pump, at the frequency ofmechanical resonance of this pulsation-smoothing unit. Thus, I have ameans of eliminating to any desired degree the pressure pulsation of anygiven frequency, by tuning the smoothing device S to resonance at thisfrequency, and by making the effective internal damping of the smoothingunit as small as necessary.

Since this smoothing device has been assumed to be resonant at twice thebasic frequency, the pressure pulsation of this frequency is virtuallyeliminated from the output pressure of the pump, and as a result, thedouble-frequency component of the discharge from the pump must alsodisappear from the flow in the external fluid circuit. This component ofthe discharge is now flowing, in effect, through the pressure-smoothingunit and thus bypassing the external fluid circuit. In reality there isno true flow through the smoothing device, since there is no connectioninternally between the high-pressure bellows and the low-pressurebellows, but because of the incompressible liquid which just fills thespace outside the bellows units but inside the container, any increasein the internal volume of one bellows must exactly equal thecorresponding decrease in the internal Therefore, the net effectobserved from the external fluid circuit is the same as if thedouble-frequency alternating component of discharge were flowing withoutimpedance through the bellows device and thus bypassing the externalcircuit.

It should be noted in passing that the motion of the crosshead 84 in thesmoothing device will bepredominantly a double-frequency simple harmonicmotion, since it responds most to this frequency of its own resonance,and its peak-to-peak excursion is limited to that which is required justto bypass the Znd-harmonic discharge component in the output of the pumpas shown by the above equation. Thus, there is no possibility of theoccurrence of dangerous amplitudes of motion within the device.

By connecting across the output conduits of the pump another smoothingdevice like the one just described, but tuned to a mechanical resonanceat four times the basic frequency, we can eliminate from the output the4thharmonic components of pressure and discharge. In similar fashion, wemay eliminate any or all of the higher harmonics of pressure anddischarge, by adding more units in parallel, each tuned to resonance atthe frequency which it is to eliminate.

It should be noted in this connection that the size of the bellows unitsin each successive smoothing device can be smaller than in the precedingdevice. Thus, in this situation, the change of volume per strokerequired for the Znd-harmonic smoothing device is 0.4244 times that ofthe pumping device, the change per'stroke of the 4th-'harmonic unit is0.08486 times that of the pumping device, etc.

To summarize, the important and novel features of the pressuresmoothingdevice of this invention are:

(1) There are'no check valves of any lcind within the unit.

(2) There is no internal passageway between one bellows and the other.

(3) The moving system is tuned to mechanical resonance at the frequencyof pressure and/ or flow pulsation which it is desired to eliminate fromthe output of the (4) The bellows-and-crosshead assembly is completelyenclosed in a leakproof enclosure, and the space outside the bellowsunits but inside the container is completely filled with anincompressible liquid having a low temperature-coeflicient of expansion,so that (a) the internal pressure acting on the bellows units istransmitted to the outer container rather than being home by the bellowsalone, and (b) the change of volume of one bellows is always constrainedto be exactly equal and opposite to the change of volume of the otherbellows, when the crosshead moves.

(5 Dampen-ing force may be introduced into the unit, if for any purposethis should be desirable, by obstructing, to a greater or lesser degree,the flow of the filler liquid around and through the crosshead as itmoves. The residual harmonic pressure pulsation in the output of thepump is determined by the amount of damping thus introduced.

Note, in connection with item 4, above, that the highpressurebellowsmust expand slightly because of its internal pressure. Thisexpansion ceases when the effective inward pressure due to the stressesin the bellows wall itself and the outside pressure of thenow-compressed filler liquid just balance the internal pressure actingon the bellows. lows must contract slightly (i.e. decrease its internalvolume), until the excess pressure acting on its outer surface is justbalanced by the stresses in its own wall and the internal pressure ofthe fluid within this bellows. If the bellows units are reasonably rigidthemselves, then these changes of volume just described are small.Further changes of volume are due entirely to the displacements of thecrosshead, and since the filler liquid is virtually incompressible andis enclosed in a leakproof, rigid housing, any such change in theinternal volume of one bellows must be exactly equal and opposite tothat of the other bellows. This is a necessary feature of the device,for if the instantaneous flow rate at the intake conduit of the fluidrectifier is not equal to the instantaneous flow rate at the dischargeconduit of the rectifier, cavitation may occur within the body of therectifier or within the pump unit itself.

It follows from the foregoing that oscillating the crosshead 15 producesa purely alternating flow in the lines 68 and 70, as indicated by thesymbols; that this alternating flow is transformed by the rectifier intoa pulsating, unidirectional flow in the discharge line 72, as indicatedby the symbols; that the pulsating, unidirectional flow in dischargeline 72 is eifective to produce a purely alternating fluid flow in ducts104 and 105 of the smoothing device S, which is predominantly asinusoidal flow of twice the pump frequency; and the alternating flow inducts 104 and 105 is effective to produce an essen-' tially steady flowin the discharge line 72 on the downstream side of its connection withthe duct 105, since the dominant component of pulsation, namely, thesecond harmonic, is virtually suppressed, and simultaneously there isproduced a pulsating unidirectional flow in duct 104 on the upstream endof its connection with duct 104. If it is desired, as many units of thistype as necessary may be added in parallel to the 2nd-harmonic smoothingdevice, each of the other smoothing devices being tuned to one of theharmonic frequencies which are normally present in the discharge of thepump. These frequencies, in this case, are the following multiples ofthe basic pump frequency: 2nd, 4th, 6th, 8th, 10th, etc.

It is clear that a smoothing device of the type just described can beused to eliminate the pulsations from the discharge of any type of fluidpump operating under steady conditions, since any such discharge can beresolved into a constant average value plus a Fourier series of harmonicvariations. It is also clear, that, if 2 harmonic variations in pressureor flow lie close enough to one another on the frequency scale, then asingle smoothing device which is tuned to some appropriate frequency ofresonance intermediate to the 2 frequencies which At the same time, thelow-pressure bel- I must be removed, can be used to suppress both theseharmonic components of the discharge.

The aforementioned principles are applicable to various other types ofsystems embodying two or more conduits in which there is an oscillatingfluid 'flow. Inthe system shown in Fig. 4 there are three identicalpumping units P1, P2, and P3 connected with a rectifying unit R and apressure smoothing device S is connected across the discharge and returnlines leading to and from an apparatus or system A the operation ofwhich requires a relatively smooth and continuous unidirectional fluidflow.

Each of the pumping units is identical to the pumping unit P abovedescribed and the same reference charac: :ters are applied to the sameparts. These three pumping units are radially disposed about a-commondrive shaft 46a and circumferentially spaced 120 apart. The shaft 46acarries a crank 45a which is connected to the driving flanges of thepumping units by rods 110, 111 and 112, as in the embodiment of Fig. 1.

The output ducts 30 of the pumping units are interconnected by lines114, 115 and 116 and the output ducts 32 are connected with conduits120, 121 and 122 whichlead to the rectifying unit R. The rectifying unit-R' comprises output passages 124, 125, 126 and input passages 124,125', 126'. The passages 124 and 124' are connected at one end to eachother and to the conduit 120 and at their other ends are connected tothe intake and discharge lines 145 and 135 through one-way check valves140 and 130 respectively. As apparent "from Fig. 4, the passages 125 and125 and the pairs of vpassages 125, 125' and 126, 126 are likewiseinterconnected and connected to the conduits 121 and 122 respectivelyand further are likewise connected through check valves 131, 14-1 and132, 142 to the intake line 145 and discharge line 135.

The pressure smoothing device S comprises a pair of opposed cylinders150 and 151 having their open ends formed with flanges between which isclamped a flexible diaphragm 154 which defines apair of expansiblechambers 155 and 156 arranged so that when one expands the othercontracts. The opposite ends of the chambers are connected by lines 160and 161 tothe discharge-and return lines 135 and 145, respectively,which lead to and from the apparatus or system A.

In operation the oscillations imparted to the crossheads of the pumpingunits producean alternating flow in the conduits 114, 1 and 116 and alsoin the output lines 120, 121 and 122, but the'c'heck valves 130, 13 1and 132 of the rectifying unit permit'only a unidirectional, pulsatingflow in the discharge line 135. Like wise the check valves 140, '14-1and 142 permit only a unidirectional flow in thereturn line v145. As aresult the main body of fluid being circulated does not flow into theinternal circuit including the pumping umts and associated lines, butrather is circulated through the rectifying unit R. Since the smoothingdevice S is connected across the discharge and return lines, it iseffective to smooth out the pulsations in the discharge line and producecorresponding pulsations in the return line on the down stream side ofits connection therewith, as above explained.

The diaphragm 154 may be of any suitable corrosionresisting metal orother material of known resilience and stifiness and the mass within thechambers 155 and 156 is primarily determined by the dimensions of thechambers and the liquid density. Although the diaphragm 154 is operativethroughout a Wide range of frequencies of the pumping units, yet for themost efflcient operation the pumping units are operated at asubstantially constant speed or frequency and a diaphragm 154 isselected that has a natural frequency of six times the normal operatingfrequency of the pumping units.

It will be noted that in both of the embodiments herein shown the entirepumping apparatus including the pumping unitsyfluid rectifiers andsmoothing unitprovides'ra completely enclosed system which may be 'madefrom any suitable material 'inertto the fluid being pumped, and thatthere are no moving parts such as impellers, drive shafts, or the likewhich come into direct contact with the fluid. Hence, the apparatus maynot only be used to pump fluids containing abrasive particles such asencountered in the coolant fluid used with machine tools,

pose of illustration and that various changes and modifications may bemade without departing irom the spirit and scope of the invention as setforth in the appended claims.

I claim:

1. In apparatus of the class described, a pump having a fluid flowopening and operative to provide an oscillating fluid flow through saidopening, an intake line for supplying fluid, a discharge line forcarrying discharged fluid, rectifying means connected to the intake anddischarge lines and to said opening to provide unidirectional fluid flowin said intake line and to provide unidirectional pulsating fluid flowin said discharge line in re sponse to operationof the pump, pulsesmoothing means for smoothing out pulsations in fluid flow in saiddischarge line including a pair of compressible chambers arranged sothat when one chamber is expanded the other chamber will becompressed,and means connecting one of the chambers in flow communication with theintake line and the other of the chambers in flow communication with thedischarge line.

2. In apparatus of the class described, a fluid pump including anexpansible chamber having a fluid flow opening, and means foralternately expanding and compressing the chamber to draw in anddischarge fluid to and from the chamber through said opening; an intakeline for supplying fluid; a discharge line for carrying dischargedfluid; rectifying means to provide unidirectional fluid flow in saidintake line and unidirectional pulsating fluid flow in said dischargeline in response to operation of the pump, the rectifying meansincluding an input passage and an output passage connected at one end ofeach to each other and .to said opening, the other ends of the input andoutput passages being connected respectively to the intake and dischargelines, and check means in each of the input and output passages; andpulse smoothing means for smoothing pulsations in fluid flow in saiddischarge line and for introducing pulsations in fluid flow in saidintake line including a pair of compressible chambers connected to eachother so that when one chamber is expanded the other will be compressedand vice versa, and means connecting one of said pair of chambers influid flow communication with said intake line and the other chamber ofsaid pair of chambers m fluid flow communication with said dischargeline.

3. Apparatus of the class described comprising pumping and rectifyingmeans having discharge and intake lines and operative to discharge apulsating unidirectional flllld flow through the discharge line and drawin a unidirectional fluid flow through the inlet line, and pressuresmoothing means comprising an enclosed chamber containing a liquid, twobellows within said chamber and arranged so that when one is expandedthe other is compressed, each of said bellows having a port, a ductconnecting one port with the discharge line and a second duct connectingthe other port with said intake line.

4. Apparatus of the class described comprising pumping and rectifyingmeans having discharge and intake lines and operative to discharge apulsating unidirectional fluid flow through the discharge line and drawin a unidirectional fluid flow through the inlet line, and pressuresmoothing means comprising an enclosed chamber containing a liquid, twocoaxially disposed bellows with closed adjacent ends within saidchamber, said bellows being arranged so that when one is expanded theother is compressed, the opposite end of each bellows having a port, aduct connecting one port with the discharge line and a second ductconnecting the other port with said intake line.

5. Apparatus of the class described, comprising two bellows, each havinga single opening at one end, a conduit connected with each opening,means for compressing one of said bellows and simultaneously expandingthe other so as to cause an oscillating fluid flow in the conduits, afluid rectifier having a discharge passage connected at one end with oneconduit, a second discharge passage connected at one end with the otherconduit, a return passage connected at one end with the first conduit, asecond return passage connected at one end with a second conduit, adischarge duct connecting the opposite ends of the discharge passages, areturn duct connecting the opposite ends of the return passages, adischarge line connected with the discharge duct, an intake lineconnected with the return duct, and check means in said passagesconjointly operative in response to an oscillatory flow in said conduitsto discharge a pulsating unidirectional fluid flow through saiddischarge line and draw in a unidirectional flow through said intake"line, two compressible chambers arranged so that when one is expandedthe other is compressed, each of said chambers having an opening, a ductconnecting one opening with said discharge line, and a second ductconnecting the other opening with said intake line so as to smooth outthe pulsations in the fluid flow in said discharge line and introducecorresponding pulsations in the fluid flow in said intake line.

6. Apparatus as set forth in claim 5, wherein balanced springs act onsaid bellows so as to oppose oscillating movement thereof, the resultantstiffness of said springs being such that the natural frequency of saidbellows conforms to the frequency of said pulsating flow.

7. Apparatus as set forth in claim 5, wherein a pair of coaxiallydisposed balanced helical springs act on said bellows so as to opposeoscillating movement thereof, resultant stiflness of said springs beingsuch that the natural frequency of said bellows conforms to thefrequency of said pulsating flow.

8. Apparatus of the class described, comprising a driving shaft, threepumping units radially disposed about said shaft and circumferentiallyspaced 120 apart, each of said pumping units having an output line,means connecting said drive shaft and pumping units so that analternating fluid flow takes place in the output lines in response torotary movement of said shaft, a fluid rectifier having a discharge lineand an intake line, said rectifier having a branch line connected witheach output opening, a duct connecting one opening with said dischargeline and a second duct connecting the other opening with the intakeline.

9. Apparatus of the class described, comprising at least one pair ofexpansible chambers, each chamber having a single output opening, meansfor compressing one of said chambers and simultaneously expanding theother so as to cause an oscillating fluid flow through each of saidopenings, a conduit connected with each opening, a fluid rectifierhaving discharge passages and return passages connected with theconduits, the discharge passages having check means permitting anoutward flow and the return passages having check means permitting aninward flow, an intake line connected with the return passages and adischarge line connected with the discharge passages the parts beingoperative to discharge a pulsating unidirectional fluid flow throughsaid discharge line and draw in a unidirectional flow through saidintake line, and pulse smoothing means including two compressiblechambers arranged so that when one is expanded the other is compressed,each of said chambers having an opening, a duct connecting one openingwith said discharge line, and a second duct connecting the other openingwith said intake line so as to smooth out the pulsations in the fluidflow in said discharge line and introduce corresponding pulsations inthe fluid flow in said intake line.

References Cited in the file of this patent UNITED STATES PATENTS2,316,278 Orshansky Apr. 13, 1943 2,348,538 Hagen May 9, 1944 2,430,723Lupfer Nov. 11, 1947 2,764,999 Stanbury Oct. 2, 1956 2,780,065 SpannhakeFeb. 5, 1957 2,811,931 Everett Nov. 5, 1957 FOREIGN PATENTS 4,270Netherlands Dec. 1, 19.19 360,628 Germany Oct. 5, 1922 425,500 GreatBritain Mar. 15, 1935 605,039 Great Britain July 14, 1948 695,556 GreatBritain Aug. 12, 1953 1,100,067 France ..1 Mar. 30, 1955

